How does bonding explain the very different properties of salt, sugar and metals?
Properties of ionic, molecular and metallic substances: relate melting point, electrical conductivity, hardness and solubility to the type of bonding and structure.
A focused Regents Chemistry answer on how bonding type explains properties: why ionic solids have high melting points and conduct only when molten or dissolved, why molecular substances are soft and low-melting, and why metals conduct and are malleable.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this topic is asking
The Core Curriculum asks you to relate the physical properties of a substance, its melting point, electrical conductivity, hardness and solubility, to its bonding and structure. This is one of the most heavily tested ideas on the Regents because it appears as both Part A recall and Part B-2 "identify the bonding from the properties" questions.
Ionic substances
Sodium chloride is the standard example: it melts above , shatters rather than bends, dissolves readily in water, and a solution or molten sample conducts electricity. The brittleness comes from the lattice: a blow that shifts the ions brings like charges next to each other, and the repulsion splits the crystal.
Molecular substances
Sugar and carbon dioxide are molecular: sugar melts at a low temperature and its solution does not conduct (it dissolves as neutral molecules, not ions), and carbon dioxide is a gas at room temperature. The contrast with ionic substances, especially the conductivity test, is exactly what Part B-2 questions probe.
Metallic substances
Metals are held together by metallic bonding, a sea of mobile valence electrons around positive ions. This explains their characteristic properties: they conduct electricity and heat in both the solid and liquid state (the electrons are always mobile), and they are malleable and ductile because the ions can slide past one another while the electron sea keeps the structure bonded. This is why a metal can be hammered into shape, whereas an ionic crystal shatters.
A comparison to memorize
| Property | Ionic | Molecular | Metallic |
|---|---|---|---|
| Melting point | high | low | usually high |
| Conducts as solid | no | no | yes |
| Conducts when molten or dissolved | yes (molten or aqueous) | no | yes (molten) |
| Hardness / form | hard, brittle | soft or gaseous | malleable, ductile |
| Solubility in water | often soluble | polar yes, nonpolar no | insoluble (reacts or stays solid) |
Try this
Q1. State whether a sample of solid sugar conducts electricity, and why. [1 point]
- Cue. No; it is molecular, with no free-moving charged particles.
Q2. Explain why metals are malleable but ionic crystals are brittle. [1 point]
- Cue. In metals the electron sea lets ions slide past one another and still stay bonded; in ionic crystals a shift brings like charges together, and the repulsion cracks the lattice.
Exam-style practice questions
Practice questions written in the style of NYSED exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Regents (Part A style)1 marksAn ionic compound conducts electricity when it is (1) a solid (2) melted or dissolved in water (3) frozen (4) in any stateShow worked answer →
A 1-point Part A item on ionic conductivity. The answer is (2) melted or dissolved in water.
In the solid state the ions are locked in a fixed lattice and cannot move, so a solid ionic compound does not conduct. When the compound is melted or dissolved in water, the ions are free to move and carry charge, so it conducts electricity. Conduction requires mobile charged particles, which a solid ionic lattice does not provide.
Markers reward recognizing that ionic compounds conduct only when their ions are mobile (molten or aqueous).
Regents (Part B-2 style)3 marksA student compares two solids: solid A has a high melting point and conducts electricity only when molten, while solid B has a low melting point and does not conduct in any state. (a) Identify the type of bonding in solid A. (b) Identify the type of bonding in solid B. (c) Explain why solid A conducts when molten but not when solid.Show worked answer →
A 3-point constructed-response item linking properties to bonding.
(a) Solid A (1 point): ionic bonding (high melting point and conducts when molten).
(b) Solid B (1 point): molecular (covalent) bonding (low melting point, nonconducting).
(c) Explanation (1 point): in solid A the ions are fixed in the lattice and cannot move, so it does not conduct; when molten, the ions are free to move and carry charge, so it conducts.
Markers reward identifying ionic bonding for the high-melting conductor, molecular bonding for the low-melting nonconductor, and explaining conduction in terms of mobile ions.
Related dot points
- Types of chemical bonds: distinguish ionic, covalent and metallic bonding in terms of electron transfer or sharing, and relate bond type to the elements involved.
A focused Regents Chemistry answer on ionic, covalent and metallic bonding: how electrons are transferred or shared, why bonds form to reach stability, the role of energy, and how to predict bond type from the elements involved.
- Intermolecular forces: describe hydrogen bonding, dipole-dipole forces and weak dispersion forces, and use them to explain trends in boiling point and the properties of water.
A focused Regents Chemistry answer on intermolecular forces: hydrogen bonding, dipole-dipole attractions and weak dispersion (van der Waals) forces, how they differ from chemical bonds, and how they explain boiling points and water's high boiling point and surface tension.
- Lewis structures and molecular polarity: draw Lewis electron-dot diagrams for simple atoms, ions and molecules, and decide whether a molecule is polar or nonpolar from its bonds and shape.
A focused Regents Chemistry answer on Lewis electron-dot diagrams and molecular polarity: how to draw dot structures for atoms, ions and small molecules, and how bond polarity together with molecular symmetry decides whether the whole molecule is polar.
- Electronegativity and bond polarity: use electronegativity differences from Table S to classify bonds as ionic, polar covalent or nonpolar covalent.
A focused Regents Chemistry answer on electronegativity difference and bond polarity: how subtracting Table S electronegativities classifies a bond as nonpolar covalent, polar covalent or ionic, and how that difference shapes the unequal sharing of electrons.
- Solutions and solubility curves: classify solutions as unsaturated, saturated or supersaturated, and use the Table G solubility curves to determine how much solute dissolves at a given temperature.
A focused Regents Chemistry answer on solutions and the Table G solubility curves: solute and solvent, saturated, unsaturated and supersaturated solutions, the factors that affect solubility, and how to read grams of solute per 100 g of water from the curve.
Sources & how we know this
- Physical Setting/Chemistry Core Curriculum — New York State Education Department (2002)
- Reference Tables for Physical Setting/Chemistry, 2011 Edition — New York State Education Department (2011)